docs: def get_mean_width(self):
          """
          Calculate and return (weighted) mean width (km) of a mesh surface.
  
          The length of each mesh column is computed (summing up the cell widths
          in a same column), and the mean value (weighted by the mean cell
          length in each column) is returned.
          """
          assert 1 not in self.lons.shape, (
              "mean width is only defined for mesh of more than "
              "one row and more than one column of points")
  
          _, cell_length, cell_width, cell_area = self.get_cell_dimensions()
  
          # compute widths along each mesh column
          widths = numpy.sum(cell_width, axis=0)
  
          # compute (weighted) mean cell length along each mesh column
          column_areas = numpy.sum(cell_area, axis=0)
          mean_cell_lengths = numpy.sum(cell_length * cell_area, axis=0) / \
              column_areas
  
          # compute and return weighted mean
          return numpy.sum(widths * mean_cell_lengths) / \
              numpy.sum(mean_cell_lengths)